Method of producing tin



July 28, 1931. A. L. .LQUENEAU 1,816f-742 METHOD OF PRODUCING TIN Filed Jan. 6. 1928 Patented July 28, 1931 AUGUSTIN LEON JEAN QUENEAU, OF NEW YORK, N. 'Y'. U

METHOD F PRODUGIN'G TIN Application led January `6, 1928. Serial No. 244,969.

The invention relates to the recovery of tin from various tin oxides, such as roasted natural cassiterite, artificial oxides, or any other form of commercial tin bearing materials in 'C the form of oxide.

In a co-pending application, Serial No.

165,720 filed February 3, 1927, which has matured into' Patent 718,378, June 25, 1929,

I have disclosed a broadly novel method of reducing certain metals. In said application I have described and claimed the invention with particular reference to the recovery of zinc. Since iiling said applicationI have made further' research and experiments and l5. have discovered that by a very similar method I can Velfectively reduce tin from its oxide.

While tin has a low melting point, 232 l C.,the reduction of 'its oxideSnO2 by carbon, as practiced in shaft and reverberator furnaces, requires temperatures of 1300o and upwards. It is a Well known fact that tin oxide is readily reduced to metallic form at a much lower temperature by various gases than in the case of carbon reduction. With pure hydrogen the reduction begins at a temperature as low as 200 C. vIt is very active above 500C. and at 10000 C. it is practically instantaneous. Care has to be taken in these reactions to remove as rapidly' as produced the gaseous product of reduction, v

water vapor, according to the reaction SnOz 2H2 Sn 2II2O.

Carbon monoxide also reduces tin oxide, but at higher temperatures than hydrogen and less actively.

The `stanniferous material is first crushed or pulverized to such a degree that 'it will pass through say a 60 meshv screen or liner and is then completely dehydrated.

As a mediumior effecting the reaction, I use a molten bath of anhydrous chlorides, preferably ternarychlorides of sodium, potassium and calcium of the general molecular formula: 50 NaCl, 20 KCl and 30 CaClZ, in which ternary salt, part of the sodium i chloride, is with advantage, replaced in varying proportion by sodium, aluminum and calcium luorides. The molecular formula given is merely an illustration and .may vary. The selected ternary salt melts at 490 C.

and above that temperature it is a mobile A liquid. It can be heated Within a wide range of temperature up to 8000-0. and over with-A out appreciable losses through volatilization. It is inert toward tin oxide or metal.

The dry tin oxide is added to the molten anhydrous mixed .salts in a mixing kettle approximately in the proportion of 100 parts of tin bearing material to parts of the molten chlorides. In this proportion a Huid pulp is readily maintained by any suitable mechanical agitator. It is in all appearances but temperature ay pulp as it is understood in dressing mill practice, the water being replaced by the molten chlorides.

The temperature'of the pulp is maintained Athroughout at about the optimum temperature, 800 C., While'a stream of anhydrous hydrogen;i preferably preheated, is forced through the mass at its lowest point. 'The vreduction of the suspended tinoxide proceeds. The liberated metal, as a liquid, drops to the lowest level of the kettle, ovving to its higher specific gravity, 7.1 a ainst the pulp gravity of about 4, while the iberated Water kettle, thus-eiciently removing the steam from contact with the reduced metal.

The accompanying drawing is a longitudinal section ythrough a suitable kettle in which the breduction is carried out.

Referring to the drawing, the reduction of the tin `oxide is carried .out in a covered kettle A, of cast iron, steel or of special alloy vapor, steam, mixes with and is carried away v.

by the unused hydrogen passing through the of the general form of a caustic pot or 'a n' Parkes process kettle. The agitationl of the pulp is maintained for lexample by an impeller or paddle d, fastened to a vertical shaft e, Supported from a frameworkv f, outside of the kettle and rotated by any suitable source of power w. A gland g is provided in the kettle cover to prevent any free passage of gas (air lor hydrogen, etc.) through the shaft opening.

The introduction of the hydrogen 1s preferably made through the vertical sha ft e which is-made hollow. This shaft is provided A able leaching apparatus.

at its upper extremity with a stuiiing box L, through whichthe stationary hydrogen gas main t' projects. The hydrogen gas escapes from the hollow shaft at its lowest point throufrhyone or more holes j for the proper disltribution of the reacting gas through the p11 p.'

The process is preferably carried on substantially at atmospheric pressure and in a continuous manner. For instance, the anhydrous molten salt is added from the aforementioned mixing kettle together with the suspended stanniferous material at a predetermined rate; the pulp entering through a metallic tube k, dipping below the level of the pulp in the reaction kettle so as to maintain an hydraulic seal. In the same manner.

an equivalent volume of the chlorides with the suspended impoverished stanniferous material outiows'from the kettle over the baied weir Z.

y The metallic tin t may be tapped at intervals through a tap hole g, by removing a plug p located at the lowest point ofthe kettle, or it may be continuously removed as formed through a lower siphon m, owing to the large difference of specific gravity between the pulp and the molten tin (lhfor the pulp against 7.1 for the molten metal). The metal is then cast in the usual slabs.

The hydrogen gas passed in excess to that absorbed by the reaction leaves the kettle through the pipe n." The hydrogen is then freed from all moisture. It is slightlycom-v pressed and it may be then passed through.

another similar kettle or kettles or stored for further use.

The overflowing pulp passes into a'second or a series of similar reaction kettles, placed in cascade. Finally, from the last kettle of the series, the issuing' pulp passes to a suit- The gangue is freed7 by counter-current washing of any chlorine compounds. It ran be then discarded as wa.` te. The aqueous solution of the recuperf..

ated chlorides is concentrated in any suitable manner, well known in the arts, and finally 'it is dehydrated'ina vacuum pan or caustic pot, or in both; the 4dry salt is then sent to a melting kettle in which'it is fusedand rendered anhydrous by boiling. It then passes to the mixingkettle for another cycle of operations. v t f The hydrogen used in the process may be o btalned from any of the well known sources ofthis gas, as from theelectrolysis of water #or from purified water-gas, coke o ven gas, etc. Or, instead of ure hydrogen, I may elect to use hydrocar on gases or vapors in the same general type of apparatus. For example, I may use hydrogen containing lgases such as water gas, town gas, natural gas and the like. Or, the hydrocarbon can be obtained from petroleum products such as crude oil, kerosene, gasolene, or from tars,

benzol, etc. 'I may also use a certairf percentage of an inert gas such as nitrogen, mixed with the hydrogen gas or the hydrocarbon.

Owing to the cracking of the injected liy-v drocarbon there is a liberation and deposition of elemental carbon inian extreme state of division and in a very active form. This carbon exerts a favorable yiniuence in maintaining the strongly reducing conditions primarily caused by the presence of hydrogen or light hydrocarbons. ducing influence of carbon and carbon com- -is adapted for treating tin oxide quite re` gardless of the manner or source from which the oxide is secured.

The foregoing description is to be construed in an illustrative ratherthan a limiting sense inasmuch as various modificationsY may be made by those skilled in theart without departure from the scope of the invention as defined in the appended claims.

WhatI claim is f 1. In the production of tin, the method which includes subjecting tin oxide to the action of a Huid reducing agent while the oxide .is held in a non-metallicmolten bath.

2. In the production of tin,`the method which includes subjecting comminutedftin oxide to the action ofI hydrogen while such tin oxide is held in suspension in a molten pulp-like chloride mass;

3. In the production of tin,.the method which consists in subjecting the dried crushed material containing tin oxide to treatment in a molten bath of anhydrous chlorides and passing a stream of hydrogen gas` through the mass.

,14. In .the productionof tin, the methody which consists in dehydrating and crushing tin oxide, feeding the same to a molten bath of anhydrous chlorides and passing hydrogen gas through the bath.

5. In the production of tin, the method which consists in subjecting dried crushed tin oxide to treatment in a molten bath of anhydrous ternary cholorides of sodium, potassium and calcium and discharging hydrogen in the bath.

6. In the production of tin, the method which consists in dehydrating and ulverizing tin oxide and subjecting 1t to t eereduc# This additive repounds. such as carbon monoxide, etc., has a ing action of hydrogen while immersed in a bath of anhydrous chlorides.

7 In the production of tin, the method which consists in providing a molten bath of anhydrous chlorides of the alkali and alkaliearth groups, adding dried crushed tin bearing material to the bath and passing hydrogen gas through Ithe bath.

8. In the production of tin, the method which consists in providing a molten pulplike bath of anhydrous chlorides, adding comminuted tin bearing material to the molten bath, passing /hydrogen gas through the bath, withdrawing the reduced metallic tin from the lower part of the'bath and discharging the spent pulp at a level higher than that of thev reduced metal.

In witness whereof, I have hereunto signed my name.

AUGUSTIN LEON JEAN QUENEAU. 

